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本文通过对甘孜满地黄土的粒度组分、石英砂的表面结构以及其它地质现象的综合研究,对甘孜黄土的成因进行了探讨。在黄土的概率累计曲线上,跃进组分和悬移组分反映明显,并以悬移组分为主。悬移组分粒径小于2～3,并以粉砂(4～8)为主,占悬移总体的94%～99%;对甘孜黄土进行扫描电镜观察表明,石英砂大部分为块状颗粒,少量(10%)呈纺锤形。采用矩阵法计算甘孜黄土的粒度参数:黄土的平均粒径(d50)为5 057～5 883,明显大于古土壤(6 120～6 549)。古土壤的标准偏差(σ)为1 513～1 973,大于黄土(1 205～1 778);黄土和古土壤的偏度系数(SK)为-0 088～0 248,显示为正偏或近于对称。黄土和古土壤的尖度系数(K)分别为0 123～1 702、0 023～0 059,前者峰形窄,后者峰形较宽。对甘孜黄土扫描电镜观察表明,石英砂大部分为方形或长方形颗粒,少量(10%)呈纺锤形。石英砂有密集的翻卷片、蛇曲脊、圆麻坑,这些结构反映了风成特征。另方面,少量石英砂显示冰川作用结构,例如大大小小的贝壳状断口、平行擦痕等。在甘孜西面、德格以南的金沙江东岸川藏公路980km路碑处,三阶地上部的黄土层中,发现3条冰楔。此外,甘孜黄土中孢粉稀少。根据上述特征推断,甘孜黄土应为冰缘风成黄土。
This paper discusses the causes of Ganzi loess by comprehensively studying the grain-size components of loess in Ganzi and the surface structure of quartz sand and other geological phenomena. On the probability cumulative curve of loess, the leaping component and the suspended component reflect obviously, and the suspended component is the dominant one. The size of the suspended component is less than 2 ~ 3 , and is dominated by silt (4 ~ 8 ), accounting for 94% ~ 99% of the total suspended. The scanning electron microscopy observation of the Ganzi loess shows that the quartz sand is large Part of the massive particles, a small amount (10%) was spindle-shaped. The matrix method was used to calculate the grain size parameters of Ganzi loess: the average d50 of loess was from 5 057 to 5 883, which was obviously larger than that of paleosol (6 120 ~ 6 549). The standard deviation (σ) of paleosol was 1 513 ~ 1 973, which was larger than that of loess (1 205 ~ 1 778). The skewness coefficient (SK ) of loess and paleosol was -0 088 ~ 0 248, Or near symmetry. The kurtosis coefficients of loess and paleosol were 0 123 ~ 1 702 and 0 023 ~ 0 059, respectively. The former had a narrower peak shape and the latter had a wider peak shape. Scanning electron micrographs of the Ganzi loess showed that most of the quartz sand was square or rectangular grains with a few (10%) spindle-shaped. Quartz sand with intensive roll film, serpentine ridge, round Ma Hang, these structures reflect the characteristics of the wind. On the other hand, a small amount of quartz sand shows the structure of glaciers, such as large and small shell-like fracture, parallel scratches and so on. In the west of Ganzi, there are 3 ice wedges found in the loess layer of the third upper ground above the 980 km road mark on the Sichuan-Tibet Highway east of the Jinsha River south of Dege. In addition, rare earth spores in the Ganzi are rare. According to the above characteristics, it is concluded that the Ganzi Loess should be the ice margin of the wind into the loess.